The iPhone Dev-Team will be releasing a new version of RedSn0w that offers pwned-DFU mode via limera1n. This will let Windows users restore to a custom IPSW.
MuscleNerd: Halloween treat: upcoming redsn0w offers pwned-DFU (limera1n) mode... Windows users can then restore to custom IPSW
Unfortunately, since PwnageTool is Mac only, Windows users still need to obtain the custom ipsw via a friend.
Update
The release will also bring back custom bootlogos to the older bootrom iPhone 3GS.
